RE: Targets are in...
Dude, I'm just glad you got them in and are shooting. You really will be amazed at how much you improve.
Your shoulder getting tired is because you are trying to hold it up w/ your muscles.....It is collapsed, if you will. Drop that shoulder down and lock it in, creating a bone on bone platform. You will hold steadier and not tire as quickly. It takes a bit of practice but is much more comfortable.